Pelviureteric junction (PUJ) obstruction is the most common cause of urinary tract obstruction in children. The majority of prenatally diagnosed PUJ obstructions resolve spontaneously, but 20–25% will worsen and require intervention 1–6. The treatment options for PUJ obstruction include open pyeloplasty, laparoscopic and robot-assisted pyeloplasty, and endoluminal balloon dilatation 7–14. It is, however, difficult to preoperatively predict the outcome in those treated surgically, and, until now, there is no reliable predictive variable. This is a preliminary study to evaluate preoperative computed tomography (CT)-urography in predicting the outcome in patients with antenatally diagnosed PUJ obstruction who were treated surgically.
Patients and methods
This is a prospective study to evaluate the value of preoperative CT-urography as a predictor of outcome in those with PUJ obstruction diagnosed preoperatively and required surgical intervention. All newborns with antenatally diagnosed PUJ obstruction were evaluated after delivery with an abdominal ultrasound, and those with a renal pelvis measuring more than 3 cm in diameter were subjected to preoperative CT-urography. The kidney size, renal pelvis size, and renal parenchyma thickness were measured and documented. All underwent open surgical Anderson-Hynes dismembered pyeloplasty. The kidney function was evaluated postoperatively with serial isotope scans every 6 months for the first year and then yearly after that until their function stabilizes. All patients were followed up postoperatively and the mean follow-up was 2.5 years (1.5–3.5 years). The final results and the outcome were correlated to the preoperative renal parenchymal thickness as measured by means of CT-urography.
This is a retrospective study and there was no need for approval.
Ten consecutive newborns with PUJ obstruction were operated on and the renal parenchymal thickness was measured preoperatively by means of CT-urography to predict the outcome. There were seven male and three female patients. Their ages at surgery ranged from 8 days to 4 months (mean=1.75 months). Eight had PUJ obstruction on the right side and the remaining two had PUJ obstruction on the left side. The mean renal pelvis size on the affected side was 4.9 cm (3.6–6.3 cm). The mean renal parenchymal thickness was 0.57 cm (0.25–1.3 cm). Four had a renal parenchymal thickness less than 0.5 cm (Fig. 1a and b). Their mean renal function on the affected side was 31.4% (12–54%). Those who had a renal parenchymal thickness of 0.5 cm or less performed poorly on follow-up isotope scan compared with those who had a renal parenchymal thickness of more than 0.5 cm (mean=14.9%; 12–19.6%) (Fig. 2a and b), compared with a mean of 44.2% (33–54%).
PUJ obstruction is the most common congenital abnormality of the urinary tract causing hydronephrosis and accounts for 80% of cases. The frequency of PUJ is about one to two cases per 1500–2000 live births. PUJ obstruction is more common on the left side than on the right and is more common in male than in female populations 14. Currently, the majority of these cases are diagnosed antenatally, and this is of importance for early diagnosis and management 1,2,4. Abdominal ultrasound and diuretic renography are used to diagnose PUJ obstruction. Recently, CT-urography and magnetic resonance urography (MRU) have been used to diagnose PUJ obstruction. A voiding cystourethrogram is used to rule out vesicoureteric reflux.
The natural course of PUJ obstruction is variable. Many patients with PUJ obstruction will have stable renal function and subsequent improvement in the degree of hydronephrosis during follow-up and observation 3,4. The main criterion for observation in cases of PUJ obstruction with significant hydronephrosis is a split renal function greater than 40% in the affected kidney by means of diuretic renography. If renography shows deterioration greater than 10% on the affected side, or a relative function of less than 40%, surgery is recommended. The other indications for surgery in PUJ obstruction include PUJ obstruction-related abdominal pain, recurrent urinary tract infection under antibiotic prophylaxis, increase in the grade of hydronephrosis on follow-up ultrasound with decrease in renal function, gross hydronephrosis with renal pelvic diameter of more than 40 mm, and bilateral severe PUJ obstruction with renal parenchymal atrophy.
The timing of surgical correction of PUJ obstruction in newborns is highly controversial. In most newborns with relatively preserved differential renal function (>40% of differential renal function), hydronephrosis is considered a relatively benign condition and can be treated conservatively and followed up. In a study by Koff and Campbell 15, ∼81 of 104 patients with PUJ obstruction were followed up for 5 years, and only seven (7%) of them ultimately required pyeloplasty, and, even in these cases, pyeloplasty successfully restored the differential renal function to predeterioration levels. This, however, is not the case always, and spontaneous resolution of hydronephrosis may not be as benign as proposed by Koff and Campbell. It has been estimated that 15–33% of patients with asymptomatic neonatal PUJ obstruction show progressive ipsilateral renal deterioration, and about one-half of them never regain the lost function with pyeloplasty 16,17. There is still no evidence that prenatal intervention in infants with either a single obstructed kidney or bilateral involvement improves the overall renal function and outcome.
The most popular procedure to treat PUJ obstruction is the Anderson-Hynes dismembered pyeloplasty. The outcome of this procedure is, however, variable and there is no definite reliable preoperative predictor of the likely postoperative outcome. Cornford and Rickwood reviewed 321 patients with antenatally diagnosed PUJ obstruction. Of these, 47 (14.6%) had undergone pyeloplasty, 26 of them had undergone early pyeloplasty because of impaired function, and 21 underwent surgery after a period of expectant management. They concluded that, in patients born with PUJ obstruction and impaired renal function, pyeloplasty failed to significantly improve the renal function, possibly because of cortical loss. In patients with antenatally diagnosed PUJ obstruction managed expectantly there is a small but significant risk for a modest loss of renal function 18. Duong et al. 19 in a review of 81 children who had PUJ obstruction found that, in children who were operated on, only impaired cortical transit was predictive of differential renal function (DRF) improvement postoperatively. Abnormal cortical transit was the only predictive factor of DRF deterioration in case of conservative approach, whereas the initial degree of hydronephrosis, or renal drainage, and the initial DRF level were not predictive of the outcome. In children who were operated on, only impaired cortical transit was predictive of DRF improvement postoperatively. Barker et al.20 concluded that severe dilatation of the renal pelvis detected on second trimester ultrasound imaging predicted a significant loss of renal function. Mild and moderate degrees of dilatation were associated with a one in three risk for functional impairment in the obstructed kidney. Ben-Meir et al.21 evaluated the relationship between initial effective renal plasma flow (ERPF) and final postsurgical outcome in patients with PUJ obstruction. The final ERPF was negatively related to age (younger children), and those with a higher preoperative ERPF recovered better compared with older children and those with a lower ERPF. A relative renal function greater than 51% in the obstructed kidney with 99m-technetium mercaptoacetyltriglycine was not always beneficial in predicting the prognosis, and may be a warning of impending decompensation in a minority of patients.
PUJ obstruction diagnosed antenatally is a heterogeneous condition permitting only broad predictions of functional outcome. The results from ultrasonography and diuretic renography to assess hydronephrosis can be inaccurate and sometimes misleading. We found CT-urography valuable not only in demonstrating the degree of hydronephrosis but also in accurately measuring the renal parenchymal thickness. The number of patients in our study is small to make definite conclusions, and further studies in this regard are important. We believe that renal parenchymal thickness as measured by means of preoperative CT-urography is an important predictor of the final outcome in patients with antenatally diagnosed hydronephrosis. MRU may be more useful in this regard as it avoids radiation, but MRU is not readily available 22–24.
Conflicts of interest
There are no conflicts of interest.
1. Josephson S. Antenatally detected pelvi-ureteric junction obstruction: concerns about conservative management. BJU Int 2000; 85:973.
2. Ulman I, Jayanthi VR, Koff SA. The long-term followup of newborns with severe unilateral hydronephrosis initially treated nonoperatively. J Urol 2000; 164:1101–1105.
3. Chertin B, Pollack A, Koulikov D, Rabinowitz R, Hain D, Hadas-Halpren I, Farkas A. Conservative treatment of ureteropelvic junction obstruction in children with antenatal diagnosis of hydronephrosis: lessons learned after 16 years of follow-up. Eur Urol 2006; 49:734–738.
4. Ylinen E, Ala-Houhala M, Wikstrm S. Outcome of patients with antenatally detected pelviureteric junction obstruction. Pediatr Nephrol 2004; 19:880–887.
5. Heinlen JE, Manatt CS, Bright BC, Kropp BP, Campbell JB, Frimberger D. Operative versus nonoperative management of ureteropelvic junction obstruction in children. Urology 2009; 73:521–525.
6. Flake AW, Harrison MR, Sauer L, Adzick NS, deLorimier AA. Ureteropelvic junction obstruction in the fetus. J Pediatr Surg 1986; 21:1058–1063.
7. Parente A, Angulo JM, Romero RM, Rivas S, Burgos L, Tardáguila A. Management of ureteropelvic junction obstruction with high-pressure balloon dilatation: long-term outcome in 50 children under 18 months of age. Urology 2013; 82:1138–1143.
8. Tan HL, Najmaldin A, Webb DR. Endopyelotomy for pelvi-ureteric junction obstruction in children. Eur Urol 1993; 24:84–88.
9. Varda BK, Johnson EK, Clark C, Chung BI, Nelson CP, Chang SL. National trends of perioperative outcomes and costs for open, laparoscopic and robotic pediatric pyeloplasty. J Urol 2014; 191:1090–1095.
10. Riachy E, Cost NG, Defoor WR, Reddy PP, Minevich EA, Noh PH. Pediatric standard and robot-assisted laparoscopic pyeloplasty: a comparative single institution study. J Urol 2013; 189:283–287.
11. Monn MF, Bahler CD, Schneider EB, Whittam BM, Misseri R, Rink RC, Sundaram CP. Trends in robot-assisted laparoscopic pyeloplasty in pediatric patients. Urology 2013; 81:1336–1341.
12. Dangle PP, Kearns J, Anderson B, Gundeti MS. Outcomes of infants undergoing robot-assisted laparoscopic pyeloplasty compared to open repair. J Urol 2013; 190:2221–2226.
13. Turner RM 2nd, Fox JA, Tomaszewski JJ, Schneck FX, Docimo SG, Ost MC. Laparoscopic pyeloplasty for ureteropelvic junction obstruction in infants. J Urol 2013; 189:1503–1507.
14. González R, Schimke CM. Ureteropelvic junction obstruction in infants and children. Pediatr Clin North Am 2001; 48:1505–1518.
15. Koff SA, Campbell K. Nonoperative management of unilateral neonatal hydronephrosis. J Urol 1992; 148 (Pt 2):525–531.
16. Ransley PG, Dhillon HK, Gordon I, Duffy PG, Dillon MJ, Barratt TM. The postnatal management of hydronephrosis diagnosed by prenatal ultrasound. J Urol 1990; 144 (Pt 2):584–587.
17. Cartwright PC, Duckett JW, Keating MA, Snyder HM 3rd, Escala J, Blyth B, Heyman S. Managing apparent ureteropelvic junction obstruction in the newborn. J Urol 1992; 148:1224–1228.
18. Cornford PA, Rickwood AM. Functional results of pyeloplasty in patients with ante-natally diagnosed pelvi-ureteric junction obstruction. Br J Urol 1998; 81:152–155.
19. Duong HP, Piepsz A, Collier F, Khelif K, Christophe C, Cassart M, et al.. Predicting the clinical outcome of antenatally detected unilateral pelviureteric junction stenosis. Urology 2013; 82:691–696.
20. Barker AP, Cave MM, Thomas DF, Lilford RJ, Irving HC, Arthur RJ, Smith SE. Fetal pelvi-ureteric junction obstruction: predictors of outcome. Br J Urol 1995; 76:649–652.
21. Ben-Meir D, Hutson JM, Donath S, Chiang D, David J. The prognostic value of relative renal function greater than 51% in the pelvi-ureteric junction-obstructed kidney on 99mtechnetium mercaptoacetyltriglycine study. Cook J Pediatr Urol 2007; 3:184–188.
22. McDaniel BB, Jones RA, Scherz H, Kirsch AJ, Little SB, Grattan-Smith JD. Dynamic contrast-enhanced MR urography in the evaluation of pediatric hydronephrosis: Part 2, anatomic and functional assessment of ureteropelvic junction obstruction [corrected]. Am J Roentgenol 2005; 185:1608–1614.
23. Jones RA, Easley K, Little SB, Scherz H, Kirsch AJ, Grattan-Smith JD. Dynamic contrast-enhanced MR urography in the evaluation of pediatric hydronephrosis: Part 1, functional assessment. Am J Roentgenol 2005; 185:1598–1607.
24. McMann LP, Kirsch AJ, Scherz HC, Smith EA, Jones RA, Shehata BM, et al.. Magnetic resonance urography in the evaluation of prenatally diagnosed hydronephrosis and renal dysgenesis. J Urol 2006; 176:1786–1792.